Observation of mixed acetylene - Nitrous oxide trimers: Infrared spectra of C2H2-(N2O)(2) and (C2H2)(2)-N2O

摘要

Infrared spectra of the lowest energy isomers of C2H2-(N2O)(2) and (C2H2)(2)-N2O were observed in the region of the nu(1) fundamental band of the N2O monomer (similar to 2224 cm(-1)) using a tunable diode laser and/or a CW quantum cascade laser to probe a pulsed supersonic slit jet expansion. One infrared band was measured for each trimer. The band for C2H2-(N2O)(2) corresponds to the out-of-phase vibrations of the pair of equivalent N2O monomers. It is blue shifted by about 10 cm(-1) with respect to the free N2O monomer. The band for (C2H2)(2)-N2O is slightly less blue shifted (centered at 2232.81 cm(-1)). It can be simulated as a predominately a-type band. In addition to the normal isotopologues, the corresponding bands for C2D2-(N2O)(2) and (C2D2)(2)-N2O were also observed. The structures of these trimers are similar to those of the lowest energy isomers of the analogous OCS - acetylene trimers reported previously, that is, a twisted barrel with C-2 symmetry for C2H2-(N2O)(2) and a distorted T-shaped acetylene dimer with a coplanar N2O beside the stem of the T for (C2H2)(2)-N2O. Here, we present our observation and experimental results, which agree well with calculations based on distributed multipole pair potentials. (C) 2014 Elsevier Inc. All rights reserved.